Examples of flat panel displays include liquid crystal displays (LCDs), organic light emitting displays (OLEDs), plasma display panels (PDPs), quantum dot panels (PDPs), field emission displays (FEDs), electrophoretic displays (EPDs) and the like. These displays include a flat display panel realizing an image in common as an essential component. Such a flat display panel has a configuration in which a pair of transparent insulating substrates are joined together such that they face each other via a layer containing an inherently luminescent or polarizing material or other optical material interposed therebetween.
In accordance with the recent trend toward large-size displays, demand for flat panel displays taking a smaller space gradually increases. Of these flat panel displays, organic light emitting display technologies are being rapidly developed.
Organic light emitting displays do not require any separate light source and include an organic light emitting diode that spontaneously emits light in each pixel, to realize display. The organic light emitting displays attract much attention as next-generation displays since they advantageously do not require light sources as well as structures for assembling the light sources with a display panel, thus having advantages of decrease in thickness and weight.
When electric charges are injected into an organic film formed between an electron injection electrode (cathode) and a hole injection electrode (anode), electrons pair with holes and the pairs then decay. At this time, an organic light emitting diode emits light.
Meanwhile, there is an increasing demand for incorporating a touchscreen into an organic light emitting display, where a site touched by the hand or separate input element is sensed and information is transferred in response thereto. Such a touchscreen is being applied by adhesion to the outer surface of the display.
Depending on touch sense methods, a touchscreen may be of resistive, capacitive and infrared sensing types. In consideration of ease of manufacture, sensing force and the like, capacitive type touchscreens attract much attention in small models.
Hereinafter, a touchscreen-integrated organic light emitting display of related art will be described with reference to the annexed drawings.
FIG. 1 is a sectional view illustrating a touchscreen organic light emitting display of related art.
As shown in FIG. 1, the touchscreen-integrated organic light emitting display includes an organic light emitting display panel 1, a touchscreen 2 and a cover window 3 laminated in this order from the bottom and includes first and second adhesive layers 15 and 25 disposed between the respect layers.
Here, the organic light emitting display panel 1 includes a substrate, a thin film transistor array having a matrix form disposed on the substrate, and an organic light emitting diode connected to each thin film transistor of the thin film transistor array, and includes a protective film and a polarizing layer that cover the top of the organic light emitting diode. In this case, the first adhesive layer 15 corresponds to the polarizing layer of the organic light emitting display panel 1.
The touchscreen-integrated organic light emitting display of related art has the following disadvantages.
First, when an organic light emitting display panel and a touchscreen are independently formed, and the touchscreen is then attached to the organic light emitting display panel, the organic light emitting display panel and the touchscreen require separate glasses, thus resulting in increased hardness and thickness, and making realization of thin and flexible organic light emitting displays impossible.
Second, the organic light emitting display panel and the touchscreen have different panel shapes, thus making processes for forming these components complicated and thus decreasing yield and price competiveness.
Third, if the touchscreen is configured as an in-cell type, a pad portion of the touchscreen faces an inside, that is, a side of a pad portion of an organic light emitting display panel. In this case, a bonding process is performed using a sealant including conductive balls. Herein, relatively small conductive balls may have contact defects due to difference in diameter between the normal conductive balls. Also, a compression level of conductive balls is changed depending on a pressure applied during bonding and contact defects may thus occur during the bonding process.